But you could try a few things:
Here is an answer from support that I got a while ago. Hope that helps:

By default, CGP uses tsl1.0 for outgoing SMTP connection.
You can add "--SMTPOutgoingTLSVersion 2" starup parameter, so that CGP will use tsl 1.1 for outgoing SMTP connection.
Adding "!mx.target-mail-server.com" to the Send Encrypted (SSL/TLS) list at Settings->Mail.SMTP->Sending would tell CGP not to establish secure
connection when sending emails.
Obviously you should use a newer CGP version - there've been some TLS fixes and additions.

Well, we see tls problems raising.
I really hope that CGP will soon introduce a function "use plain if TLS does not work".

CG could not send a message:
22:06:55.705 3 SMTP-000424(tucsonwomenschorus.org) failed to establish a secure connection with [216.222.193.110]:25. Error Code=TLS record version is not 3.x

What does the error about TLS mean?
What is the best way to correct it?

--
James Moe
moe dot james at sohnen-moe dot com
520.743.3936
Think.

#############################################################
This message is sent to you because you are subscribed to
the mailing list <CGatePro@mail.stalker.com>.
To unsubscribe, E-mail to: <CGatePro-off@mail.stalker.com> To switch to the DIGEST mode, E-mail to <CGatePro-digest@mail.stalker.com>
To switch to the INDEX mode, E-mail to <CGatePro-index@mail.stalker.com> Send administrative queries to <CGatePro-request@mail.stalker.com>